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This article explains critical safe-construction details for decks and porches, including avoiding deck or porch collapse and unsafe deck stairs and railings. This article includes excerpts or adaptations from Best Practices Guide to Residential Construction, by Steven Bliss, courtesy of Wiley & Sons. Also see our review of that book. Our page top photo shows a hybrid deck structure that encompasses a boat. No fasteners were found securing the boat to the deck however.

Details about choosing the right structural connectors for decks and how they should be installed are at Fasteners, Structural for Decks. At Fasteners, Nails, Screws, Hidden, for Decks we discuss choosing the proper nail, screw, or hidden fastener for fastening deck boards, railings, or joist hangers. Spans, sizes and spacings for deck joists and deck beams are discussed in detail at FRAMING TABLES, SPANS for DECKS and are shown in Table 4-7 and Table 4-8. Basic building framing information is found at FRAMING SIZE & Spacing, Age, Types.

Also see Deck Framing Tables, Spans and Deck & Porch Connections: Ledger Boards. And see Preservative-Treated Framing Lumber. see Rot-Resistant Deck Lumber & Flooring for a discussion of lumber and flooring alternatives to preservative-treated wood.

This article series discuss best porch & deck construction practices, including choice of framing materials, decking or flooring choices & installation, how to select and use deck and porch structural and flooring fasteners, actual deck & porch framing construction details & connections, deck joist & beam span tables, how to build leak-proof rooftop decks, construction of covered & screened porches, deck & porch railing construction & materials, choices of finishes and stains for decks & porches, and past & current deck lumber preservative treatments with related health & environmental concerns.

© Copyright 2012 InspectAPedia.com, Daniel Friedman, Steve Bliss, Wiley & Sons, All Rights Reserved. Information Accuracy & Bias Pledge is at below-left. Use page top links to major topics or use links at the left of each page to navigate within topics and documents at this website. Green links show where you are in a document series or at this website.

A Quick Photo Guide to Steel Connectors Used in Deck Construction

As described in Best Practices Guide to Residential Construction, Chapter Four, Best Construction Guide for Building Decks and Porches: For the strongest connection of beam to post, place the support beam directly on top of the posts, rather than bolting them to the side, so the full load is transferred to the posts. To keep the post in place and to prevent any twisting or shifting, the connection should be reinforced with steel strapping, a steel connector, or a treated plywood cleat.In general, notching a 4x4 post will leave too little wood for an adequate connection. A double 2x beam can rest on a notched 6x6 post, as shown. For the strongest connection of joists to the support beam, the joists should sit on top of the beam.

For a more streamlined appearance, however, joist hangers are acceptable. Make sure the hangers and nails are approved by the manufacturer for use with the new types of pressure- treated wood (ACQ or ACZA) and fill all the holes in the hangers with properly sized nails. In general, nail into the joists with 1 1/2-inch joist-hanger nails and nail into the beam with 10d to 16d common nails, as specified by the hanger manufacturer.

Deck Joist & Beam Sizing Tables & A Quick Rule of Thumb for Sizing Joists

Spans, sizes and spacings for deck joists and deck beams are discussed in detail at FRAMING TABLES, SPANS for DECKS and are listed in Table 4-7 and Table 4-8.

Guide to Selecting the Proper Deck & Porch Structural Fasteners, Screws, Nails, Lags, Bolts

New Wood Preservatives and Their Corrosion Effects on Deck Nails, Screws, Connectors & Fasteners

Also see Preservative-Treated Framing Lumber.

Our photo, left, shows three fasteners we have found used with steel joist hangers. This photo shows the heads of each of these fasteners. Because the new wood preservatives ACQ (alkaline copper quat) and copper azole contain significantly more copper than the older CCA-treated lumber, they are estimated to be two to four times more corrosive to metals and galvanized coatings than the CCA they are replacing. Hot dipped galvanized nails: At bottom is a 1.5" long hot-dipped galvanized nail made by Simpson, and discussed just below. This is the proper fastener to use with galvanized steel joist hangers. Drywall screws: In the middle is a 1.5" drywall screw. These screws are tempting to use because they are available, easy to install, do not require drilling. We have inspected decks constructed entirely using interior drywall screws for both decking and for structural connections and joist hangers. Do not do this. This is an improper fastener that will fail and risks catastrophic deck collapse. Stainless steel utility screws: At the top is a 1 1/4" stainless steel screw used by a contractor to secure joist hangers when building the deck shown at the top of DECK & PORCH CONSTRUCTION. Although this screw is also made by a company that makes structural fasteners, a quick look at the company's specifications for this screw revealed that the manufacturer specifically advised that this screw was not a structural fastener and should not be used with steel framing connectors. The contractor removed the screws and used the proper fasteners instead. Stainless steel, galvanized, as well as proprietary-coating surfaced construction screws for use with treated lumber are available and of course are fine if used as recommended. But not the two screws shown in this photo and removed from decks we inspected.

Most treatment manufacturers recommend that fasteners and hardware in contact with the new treated wood be stainless-steel, heavily coated hot-dipped galvanized, or proprietary fasteners tested and approved by the manufacturer.

Hot-Dipped Galvanized Nails for Treated Lumber Decking

Stainless Steel Nails & Screws for Decks in Salt-Exposed or Wet/Humid Climates

In very wet or humid climates, or in areas subject to salt-water spray or deicing salts, stainless steel is the best choice. Stainless steel is also recommended for tropical hardwoods, which tend to cause staining with coated nails. Both types 304 and 316 stainless steel have been tested for use with the new wood preservatives ACQ and copper azole. Type 304 is suitable for above- ground applications. Type 316 is recommended in areas subject to salt or salt water.

Watch out: Never use stainless steel in contact with galvanized steel, as the galvanized coating will quickly corrode. Where fasteners such as nails, bolts, or lags are in contact with metal connectors, use the same metal for bot

Proprietary Deck Screw or Nail Coatings

If using one of these fastener types, make sure that it is recommended by the manufacturer for the specific type of decking being installed.

Aluminum Deck Nails

Best Practices Guide to Residential Construction continues:

Watch out: Do not use aluminum fasteners, connectors, or flashings in contact with pressure-treated wood. The copper-based waterborne preservatives will cause corrosion and premature failure.

Also see Preservative-Treated Framing Lumber.

Hidden Deck Fasteners for Deck Boards

Over time, face-nailed deck fasteners may loosen, stain the wood decking, or lead to splitting and water penetration. Particularly with higher-end decking materials, such as tropical hardwoods, more customers are opting for hidden fastening systems (see Deck & Porch Products, Manufacturers).

Each system is proprietary, and some require proprietary tools supplied by the fastener manufacturer. Some suppliers of hardwood decking recommend a specific fastener for their product and may sell the fasteners along with the decking. There are two types of systems. One, such as Deckmaster® (Grabber Construction Products), uses a right-angle bracket that fastens to the tops of the joists and screws into the underside of the decking. These are easiest to install if the installer has access from below the deck.

The other type uses individual fasteners that fit between adjacent decking planks and screw down into the top of the joist. These typically attach to the edges of the decking planks with clips or prongs.

A variation on this type called Eb-Ty (Blue Heron Enterprises) fits into slots cut into the edges of adjacent deck boards with a plate jointer (see Figure 4-5 below).

The biggest concern with hidden deck fasteners is whether they are strong enough to resist the tendency of deck boards to warp or twist. For that reason, they are best used with premium decking products, which are dimensionally stable. Tropical hardwoods and composite decking are good candidates for hidden fasteners.

-- Adapted with permission from Best Practices Guide to Residential Construction.

Guide to Selecting the Proper Deck or Porch Floor Decking Fasteners

Whether using nails or screws, make sure to choose a product that is up to the task both structurally and aesthetically. In general, screws are more expensive to buy and install, but often they make for a neater job with fewer callbacks due to boards popping up. Construction adhesives specially formulated for treated wood may be used in conjunction with nails or screws.

Nails for Use with Deck Floors - Decking

If the decking is to be nailed, use either spiral-, twist-, or ring-shanked nails to resist pullout. When using pressure-treated wood, the fasteners should be either hot- dipped galvanized, meeting ASTM A153, or stainless steel Type 304 or higher (see New Preservatives and Corrosion, above and see Preservative-Treated Framing Lumber).

Galvanized nails sometimes cause discoloration with redwood, cedar, and tropical hardwoods, so stainless steel is a safer choice with these materials. Aluminum nails are also an option for redwood or cedar, but they should not be used with pressure-treated wood.

The bigger the head, the better the hold-down power. At a minimum, use a casing nail, preferably a common. Some manufacturers sell special decking nails with a head size in between the two. For 5/4" decking use a 10d (3-inch) nail. For thicker decking use a 16d (3 1/2") nail.

Decking Spans for deck flooring are shown in the Table 4-4 below.

Screws for Use with Deck Floors - Decking

Power-driven screws are more expensive and a little slower to install, but they are the best choice since they do a better job of holding down the decking and are more easily removed for repairs. For treated wood, use either hot-dipped galvanized screws that meet ASTM A153, stainless-steel multipurpose screws, or specialty decking screws with proprietary coatings tested and approved for use with the new types of wood treatments.

Multipurpose screws have a thicker shank and courser thread than drywall screws, giving them greater strength and better holding power. Some specialized decking screws also have cutting nubs under the head for self-countersinking in wood.

Others have special concave “pancake” heads for composite decking. The composite-decking screws leave a crisp hole in the decking surface without the typical pucker of excess material (mushrooming) around the screw head (see Figure 4-4 below).

-- Adapted with permission from Best Practices Guide to Residential Construction.

Also see DECK COLLAPSE Case Study (collapse of a new code-approved deck) and DECK FLASHING LEAKS, ROT Case Study for an example of an older deck with rot and collapse due to improper construction and missing building flashing.

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Technical Reviewers & References

• InspectAPedia.com^® - Daniel Friedman - Publisher & Editor.
• Steven Bliss served as editorial director and co-publisher of The Journal of Light Construction for 16 years and previously as building technology editor for Progressive Builder and Solar Age magazines. He worked in the building trades as a carpenter and design/build contractor for more than ten years and holds a masters degree from the Harvard Graduate School of Education. Excerpts from his recent book, Best Practices Guide to Residential Construction, Wiley (November 18, 2005) ISBN-10: 0471648361, ISBN-13: 978-0471648369, appear throughout this website, with permission and courtesy of Wiley & Sons. Best Practices Guide is available from the publisher, J. Wiley & Sons, and also at Amazon.com.
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Use links just below or at the left of each page to navigate this document or to view other topics at this website. Green links show where you are in our document or website.

DECK & PORCH CONSTRUCTION
Deck Construction Best Practices
  Deck Beams & Girders
  Deck Piers & Posts
  Deck & Porch Connections: Ledger Boards
  Deck Framing Tables, Spans
  Deck Flashing at Building
  DECK FLOOR & STEP CUPPING
  Deck Board Gaps, Spacing Guide
  Deck & Porch Steps or Stairs
  Deck & Porch Railings
  Deck & Porch Products, Manufacturers
  Fasteners, Nails, Screws, Hidden, for Decks
  Fasteners, Structural for Decks
  Finishes, Coatings, Stains for Decks
  Porch Construction & Porch Screening
  Preservative-Treated Framing Lumber
  Rooftop Deck Construction
  Rot-Resistant Deck Lumber & Flooring
  Synthetic Deck Lumber: Composite, Plastic, Vinyl
DECK COLLAPSE Case Study
DECK FINISHES COATINGS PRESERVATIVES
DECK FLASHING LEAKS, ROT Case Study
DECKS, ROOFTOP CONSTRUCTION

Books & Articles on Building & Environmental Inspection, Testing, Diagnosis, & Repair

• Our recommended books about building & mechanical systems design, inspection, problem diagnosis, and repair, and about indoor environment and IAQ testing, diagnosis, and cleanup are at the InspectAPedia Bookstore. Also see our Book Reviews - InspectAPedia.
• Best Practices Guide to Residential Construction, by Steven Bliss. John Wiley & Sons, 2006. ISBN-10: 0471648361, ISBN-13: 978-0471648369, Hardcover: 320 pages, available from Amazon.com and also Wiley.com. See our book review of this publication.
• Decks and Porches, the JLC Guide to, Best Practices for Outdoor Spaces, Steve Bliss (Editor), The Journal of Light Construction, Williston VT, 2010 ISBN 10: 1-928580-42-4, ISBN 13: 978-1-928580-42-3, available from Amazon.com
• Manual for the Inspection of Residential Wood Decks and Balconies, by Cheryl Anderson, Frank Woeste (Forest Products Society), & Joseph Loferski, October 2003, ISBN-13: 978-1892529343, $39.00 at Amazon.com or at the InspectAPediaBookstore
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